The present invention relates to color liquid crystal display arrangements and, more particularly, to color liquid crystal display arrangements which can be driven at a low duty cycle and can provide images of high quality.
Liquid crystal display arrangements for displaying color images include a color filter set in which three filters for three different colors, i.e., red (hereinafter referred to as "R"), green ("G") and blue ("B"), are provided on a transparent substrate for every image pixel, and a guest/host crystal type containing a two-color dye dissolved in a host liquid crystal.
FIG. 5 is a cross-sectional view showing one pixel portion of a color liquid crystal display arrangement having color filters. In FIG. 5, a liquid crystal layer 1 formed of a twist nematic-type material or the like is confined between two transparent substrates 4 and 5. A transparent electrode 6 and an orientation film 7 are mounted on the side of one transparent substrate 4 facing the crystal layer 1. On the side of the other transparent substrate 5 facing the liquid crystal 1, R, G and B color filters 10R, 10G and 10B, respectively, and electrodes 9R, 9G and 9B corresponding to the color filters 10R, 10G and 10B are mounted, and black masks 11 are provided between pixel electrodes. In addition, an orientation film 8 is located on the above components. Two polarizing plates 2 and 3 are disposed on the outer sides of the transparent substrates 4 and 5 opposite the liquid crystal layer sides.
The color filters 10R, 10G and 10B are arranged in one of the several patterns shown in plan view in FIGS. 6(a)-6(d), that is, the color filters 10R, 10G and 10B may be disposed in a mosaic type of arrangement shown in FIG. 6(a), in which the color filters are sequentially shifted in position; a triangle type of arrangement shown in FIG. 6(b); a stripe type of arrangement shown in FIG. 6(c); or they may be disposed in a four-pixel type of arrangement shown in FIG. 6(d) or the like.
It will be apparent from studying FIGS. 6(a), 6(b) and 6(d) that, when the R, G and B color filters are arranged alternately in a mosaic manner, the wires used to connect electrodes of the same color together cannot be arranged so that they do not cross each other. If the wires used to connect the electrodes for R, G and B cross one another, however, then both of the colors corresponding to the crossed wires are turned on in the crossing portions thereof. In addition, the wires must be arranged to cross at two levels separated by an insulation film to prevent the two wires from being short-circuited, which greatly increases the production time and also lowers the reliability of the display arrangement. Therefore, to drive a liquid crystal display device in which this color filter arrangement is provided, the electrodes corresponding to the color filters arranged in a matrix manner are connected in a row or column direction and a periodic drive is carried out which applies a pulse voltage for every row or column of image pixels. For example, if a liquid crystal display panel has an array of 24.times.24 pixels and each pixel requires three color electrodes, R, G and B, when the electrodes are provided for every row or every column of pixels, then 24.times.3=72 electrodes are necessary, which in turn requires a high duty cycle, i.e., 1/72, for each pixel color.
However, as the duty cycle increases, the brightness difference between adjacent display pixels to which a voltage is applied and nondisplay pixels to which no voltage is applied is decreased. As a result, a clear image cannot be obtained and the quality of display is reduced.
On the other hand, as shown in FIG. 6(c), in a stripe-type arrangement in which the color filters of the same color are arranged in columns, if the electrodes in each column are connected with one another and corresponding wires extend away from the display screen so that different wires cross one another only outside of the display area, then only three terminals are required to connect the electrodes corresponding to the same color for the pixels formed on the transparent substrate, i.e., R, G and B electrode terminals. However, because the filters of the same color follow one another in each column, a partial color display is produced and, in particular, when two or more colors are mixed together, a uniform mixed color cannot be obtained.